This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-295270, filed Sep. 29, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an electrophotographic apparatus, particularly to an electrophotographic apparatus using liquid developer.
A liquid electrophotographic apparatus using liquid developer dispersing toner particles in liquid carrier, is provided with an advantage which cannot be realized by a dry process electrophotographic apparatus.
A liquid electrophotographic apparatus is provided with following advantages in comparison with a dry process electrophotographic apparatus.
1. High picture quality can be realized since an extremely fine toner particles of sub micron size can be used.
2. A sufficient picture density is provided by a small amount of toner particles and therefore, the apparatus is economical and can realize texture comparable to that in printing (for example, offset printing).
3. Toner particles can be fixed to paper at comparatively low temperature and therefore, energy conservation and high-speed output can be realized.
Meanwhile, according to the conventional electrophotographic technology using liquid developer, there are several problems. One of the problems is caused by using liquid carrier for dispersing toner particles. That is, a petroleum species liquid is normally used for the liquid carrier and therefore, there is a concern of contaminating the environment.
There are disclosed electrophotographic apparatus that contain improvements in regard to the problem of contaminating the environment, for example, Japanese Patent Laid-Open No. 320619/1996 and Japanese Patent Laid-Open No. 114254/1997.
According to the electrophotographic apparatus, there is adopted a system of transferring a toner image formed on a surface of a photosensitive roller onto paper by electrophoresis in a state in which liquid carrier is present on the surface of the photosensitive roller. Further, the paper with the toner image transferred is carried to a fuser and the toner image is fixed onto the paper by heat fixing. At this moment, the liquid carrier absorbed in the paper is evaporated by heat in heat fixing.
The electrophotographic apparatus is provided with liquid carrier absorbing chamber for covering the fuser. The vapors of the liquid carrier produced by the fuser is sucked by the liquid carrier absorbing chamber and recovered to thereby prevent the vapors from leaking to outside of a cabinet of the liquid electrophotographic apparatus.
Further, according to Japanese Patent Publication No. 17950/1983, a fixing and drying chamber having a paper discharge port is constituted by an airtight structure as much as possible and the inside of the fixing and drying chamber is maintained under negative pressure to thereby prevent a vapor of the liquid carrier from leaking from a gap of the fixing and drying chamber.
That is, conventional technology of preventing leakage of liquid carrier is executed with regard to liquid carrier adhered to paper.
Meanwhile, researches are carried out on technology of providing an image having a higher accuracy by reducing disturbance of the image transfer by transferring a toner image from a photosensitive roller to a recording medium by utilizing adhering force of toner particles.
According to the system, for example, after evaporating almost all of liquid carrier present at a surrounding of a toner image formed on a surface of a photosensitive roller by blowing drying gas, the toner image is transferred to an intermediate transfer roller arranged to be in contact with the photosensitive roller, further, the toner image is transferred from the intermediate transfer roller to paper by bringing the toner image in contact therewith. At this occasion, viscoelasticity is provided to toner particles for forming the toner image by heating the intermediate transfer roller.
According to the system, the vapor of the liquid carrier is produced at two locations of the surface of the photosensitive roller blown with the drying gas and at the surface of the heated intermediate transfer roller.
A method of recovering the vapor of the transfer system utilizing adhering force of toner particles, that is, the liquid electrophotographic apparatus producing the vapor at plural locations, has not yet been investigated sufficiently and, for example, when mechanisms of recovering the vapor are arranged at respective locations of producing the vapor, there is a problem that the liquid electrophotographic apparatus is becoming large-sized.
An object of the present invention is to provide an electrophotographic apparatus which prevents vapor of the liquid carrier produced inside of a cabinet from leaking to outside of the cabinet.
According to a first aspect of the present invention, there is provided an electrophotograpic apparatus using liquid developer comprising: a latent image holding member to form an electrostatic latent image on a surface of the latent image holding member; a development unit which develops the electrostatic latent image by the liquid developer containing liquid carrier and toner particles, and forms a toner image on the surface of the latent image holding member; a gas supply unit which supplies gas to evaporate a part of the liquid carrier and generates a vapor of the liquid carrier; a heater which heats a region in which the toner image is formed; an image transfer unit which transfers the toner image from the latent image holding member to a recording medium; a cover which covers the latent image holding member, and leads the gas with the vapor of the liquid carrier to the region; a recovery system which collects the gas with the vapor of the liquid carrier in the region.
According to a second aspect of the present invention, there is provided an electrophotograpic apparatus using liquid developer comprising: a latent image holding member to form an electrostatic latent image on a surface of the latent image holding member; a development unit which develops the electrostatic latent image by the liquid developer containing liquid carrier and toner particles, and forms a toner image on the surface of the latent image holding member; a gas supply unit which supplies gas to evaporate a part of the liquid carrier and generate a vapor of the liquid carrier; an intermediate transfer body which transfers the toner image from the latent image holding member to a recording medium and heats the region in which the toner image is formed; a cover which covers the latent image holding member, and leads the gas with the vapor of the liquid carrier to the region; a recovery system which collects the gas with the vapor of the liquid carrier in the region.